Organic thin-film transistors (OTFTs) using cross-linked olefin polymer as a gate insulator were fabricated on a plastic film. An olefin polymer layer was formed by spin-coating and baking at temperatures below 150°C. Pentacene was used as an organic semiconductor layer. The fabricated OTFTs with a short 5-μm-long channel showed a mobility of 0.1-0.2 cm2/Vs and a current ON/OFF ratio of 107. These OTFTs also exhibited good stable performance in the atmosphere. On the basis of the results, we fabricated a 5 inches OTFT-driven flexible active-matrix organic light emitting diode (AMOLED) display. The gate insulator, some metal wirings and electrodes on the OTFT backplane were formed on the plastic film by photolithography. After fabrication of the OTFT backplane, OLED layers were formed by vacuum deposition through a shadow-mask. Clear color moving images were observed on the flexible display even when it was bent.

The structure and configuration of threading dislocations (TDs) in AlN films grown on (0001) sapphire by metal–organic vapor phase epitaxy (MOVPE) were characterized by high-resolution transmission electron microscopy (HRTEM). It was found that the TDs formed in the films were mainly the perfect edge dislocations with the Burgers vector of b = ⅓〈11¯20〉. The majority of the edge TDs were not randomly formed but densely arranged in lines. The arrays of the edge TDs were mainly observed on the {11¯20} and {10¯10} planes. These two planes showed different configurations of TDs. TD arrays on both of these planes constituted low-angle boundaries. We suggest that these TDs are introduced to compensate for slight misorientations between the subgrains during the film growth.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Bicrystal experiments were performed to investigate atomic structures and high-temperature creep properties of [0001] symmetric tilt grain boundaries in Al2O3. Al2O3 bicrystals with Σ7, Σ31 and Σ39 boundaries were fabricated by a diffusion bonding technique, and their atomic arrangements at the grain boundary cores were analyzed by high-resolution transmission electron microscopy (HRTEM), in combination with static lattice calculations based on two-body ionic potentials. Compressive creep tests were also conducted to examine the behavior of grain boundary sliding for the above bicrystals. It was found that the behavior of grain boundary sliding depends on the grain boundary characters, whereas the trend of grain boundary sliding was not related to their Σ values. In contrast, HRTEM observations showed that the Σ31 boundary exhibiting the highest sliding rate has open spaces at the boundary core. Since grain boundary diffusion is expected to accommodate strains at grain boundary cores during sliding, it is likely that such open spaces give rise to high diffusivity at the grain boundary core, which results in the rapid grain boundary sliding of Σ31.

YBa2Cu3O7−y(Y123) and Nd1+xBa2−xCu3O7−y (Nd123) films were deposited by the metalorganic deposition method, and the growth mechanism of these films was investigated by high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy. The Y123 and Nd123 films were prepared by spin-coating LaAlO3 (001) and SrTiO3 (STO) (001) substrates, respectively, with solutions including trifluoroacetates. Then, the samples were heat treated at 673 K in a humid O2 gas flow to form amorphous precursor films. Finally, the precursor films were heated at higher temperatures for 0–30 min in a humid Ar/O2 gas flow and cooled rapidly from those annealing temperatures. It was found that CuO crystals with a size of 10–20 nm are segregated in the Y123 and Nd123 amorphous precursor films. In the Y123 quenched film prepared by cooling the precursor film rapidly after the heat-treatment at 1048 K for 30 min, a polycrystalline film including Y2Cu2O5, BaF2, and CuO crystals was found to be generated on the c-axis-oriented Y123 film. In contrast, in the Nd123 quenched films, (NdBa)2CuO4(Nd201) phase was found to be formed first on the surface of the STO substrate. In conclusion, the c-axis-oriented Y123 film is formed by diffusion and reaction of Y2Cu2O5, BaF2, and CuO crystals, and the Nd201 phase reacts with BaF2 and CuO crystals in a humid atmosphere to form a c-axis-oriented Nd123 film.

Grain boundary structure was examined in 0.1 mol% TiO2-excess BaTiO3 by high-resolution electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). Their grain boundaries were mostly faceted with {210} type habit. The faceted boundaries were characterized to be associated with an extra Ti–O2 bond with the rutile-like structure. The grain growth behavior in a small TiO2-excess BaTiO3 is discussed from the viewpoint of grain boundary structure.